Take another look at the tail light bulbs, sometimes the filament for the brake light can short across to the other one. Had it happen once when everytime I braked the sidelights and dash ilumination came on
After two or three days disassembling every light fitting, unwrapping the loom in any obvious rubbing points, wiggling wires with multimeters attached, I couldn’t find a sodding thing.
Since everything was apart anyway I just rewired the RHS side/tail lights.
24 hours down so far with no popped fuses, once a week has gone by I’ll consider it a success